Computing instrument



LE Roy' 1,. LEISHMAN. COMPUTING INSTRUMENT. FPLIGATNN FILED Dec. 1s. 191.1. nENEwED sEPT.15. 1922.

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iaiinai LE ROY J'. LEISHIJIAN,' OF Ofi-DEN, UTAH.

COMPUTING INSTRUMENT.

Application led December 18, 1917, Serial No. 207,778. Renewed September 15, 1922.

To all '107mm t may concern.'

Be it known that l, Ln ROY J. Lnisiiiran, a citizen of the United States, residing at ('lgden, in the county of lVeber and State ot 'lltaln` have invented certain new and useful Improvements in Computing Instruments, of which the following is a full, clear, and exact description oit the same,` reference being had to the accompanying drawing, forming part of this sp'ecilication.

lhis invention relates to an instrumentfor performing various mathematical operations, such as multiplication, division, finding diameters of circles, number of degrees in an arc, etc., and has for its general object the increase ot utility in devices of this nature.

vThe drawing shows the preferred form of my device, which consists of a transparent right angle triangle 1 of Xylonite or similar material, having a central semi-circular opening 2, the curved edge of which is graduated as at 3 into degrees, the graduations, running, as usual inboth directions -from the diameter a of the circle, this diameter forming the base of the opening 2, and having its center marked as at rllie base 6, and altitude 7 o'l` the triangle are each graduated in any desired way, beginning at the apex 8 of tlie right angle as for example, in centimeter-s 9, on the short edge, and in inches along the longer edge, the inches being sub-divided partly into tenths as at 10 and into sixteenths as at 11.

.Between the centimeter scale and the centrai opening l provide means for ascertaining the diameter o'll the circle oi which au arc is known. This consists of a pair ot' crosses 12 and 13 and a series of indicating lines lll each corresponding to .a certain sized circle, so that when the instrument is laid over a given arc so that the two crosses each rest directly on the arc, the diameter of the circle may be read directly in the scale 15, at the end of the line 14 which touches the arc. Preferably I provide a set of such means, consisting of two, as shown in the drawing', or a greater number if desired.

Serial No. 588,482.

On the liypothenuse 16 of the triangle is shown a logarithmic scale 17 extending to the edge of the instrument, and a sine scale 1S between that and the base oil diameter olf the degree scale. These scales are used in inding the number oit degrees in an arc, as follows; measure the chord (the distance from one end of the arc to the. other, straight across) using either scale l0 or 11, and iind the figure denoting this chord or base of the segment, upon the logarithmic scale 1T. For example, let us suppose the given arc when placed under the points l2 and 13 rose to midwayv between the third and fourth line ll troni the bottoni, indicating a diameter ol 34- inches, and that the distance trom tip to tip of the arc, when measured by scale 1() is shown to be 2.410 inches: Now iind the point Q40 on scale 17 corresponding to 2.40 and place a pencil mark at such point and a similai' pencil mark at 325 corresponding` to the diameter 39E. Now move the aicascope slightly towards you, sothat the marks will appear under the sine scale and to the leit so vthat the pencil mark that was at 825 is now at on the scale 18, and read the figure under the second mark, i; e. the one that was at This ligure will be found to be el@ which, multiplied by 2, gives as the correct answer, the first figure, i711-, indicating halt' the number or' degrees in the arc.

l. claim:

9i straight edged ilal sheet ciE transparent material having thereon tivo juxtaposed scales, one a logarithmic scale on said edge and the other a sine scale parallel thereto and so proportioned that the. indications on the sine scale will represent the angles whose sines are represented by the indications of the logarithmic scale. whereby when marks are made on aflat surface in accordance with the logarithmic scale on said edge the sheet or' transparent material may be shifted to make such marks visible in line With said sine scale.

LE ROY J. LEISHMAN. 

